The present invention relates broadly to a process for obtaining nutrients from cattle manure, and, more particularly, to a process and system for recovering proteins and proteinaceous materials, fats, sugars and starches from cattle manure, and to convert a certain amount of the starches and celluloses therein to usable sugars.
It is conventional practice in the raising of cattle in the United States and certain other countries, to confine them in so-called feed lots or feed yards, where they are fed high-value feed mixes enriched with proteins, carbohydrates, fats, vitamins and minerals to achieve a relatively rapid gain in weight of the cattle. For example, such feed lots or feed yards may often contain as high as 2,000 to 50,000 head of cattle in a relatively small area. Hundreds of such yards exist in the United States alone and correspondingly large numbers of such lots or yards are presently in use in Japan and Europe.
Studies have shown that cattle are relatively inefficient in converting their food, and particularly the high value feed mixes, to useful meat and tissue, and, in fact, it has been shown that an average of 18 pounds (dry weight) per day of the high-value feed mixes must be fed to each animal for maintenance and to produce a daily average increase in weight of 11/2 to 23/4 pounds. Moreover, the average animal voids approximately 6 pounds of dry weight per 24 hour period. From this it is clear that 30 to 40% by weight of the food value passes through the cattle and is present in its manure.
To date the manure has been merely removed periodically from the confined areas and stockpiled, pressed into blocks, and in some cases a small amount has been used on the local fields as humus, for example. Otherwise, the nutrient value in the manure has been completely lost.
In addition, the necessary removal of manure produced in the vast quantities that it is, represents a serious ecological problem. For example, estimates are that each cattle produces some 2,000 pounds in dry weight of manure on an annual basis, which amounts to some 17 to 20 million tons of dry manure in the 600 to 800 feed yards that exist in the United States. Moreover, the dairy industry in the United States by itself produces approximately 10 million tons of dry manure each year. Manure, when it is stockpiled, particularly adjacent rivers or streams, may pollute the streams and, of course, the obvious odor pollution of the atmosphere is generally offensive. Still further, flies, insects and other vermin readily propagate in manure. It is, therefore, a desideratum not only to recover whatever nutrients may be available in cattle manure, but also to eliminate the large quantities of manure that accumulate each year in a non-polluting manner.